The goals of this study are to develop optimal experimental and analytic techniques for the application of quantitative radiocardiography to the non-invasive study of left ventricular function using a gamma emitting tracer and an Anger camera, and to establish statistically the significance of results available from these investigations by comparing them with results obtained at catheterization. The quantitative study of this important new technique is a logical continuation of research initiated at the University of California at Berkeley by a team which included the principal investigator. 1) Integration of gamma camera and data acquisition systems, and development of appropriate data reduction logic. 2) Verification of the integrated camera and data acquisition system by means of a known mechanical model of the cardiopulmonary circulation, with the goal of precisely defining parameter sensitivity and accuracy. 3) Concurrent development of a mathematical model of the central circulation for the purpose of forming a rational basis for the analysis of experimental data, and for providing a means of predicting and analyzing tracer response in patients with ventricular failure. 4) Study of patients with acute myocardial infarction by the serial radiocardiographic measurement of end diastolic and systolic right and left ventricular volumes, ventricular ejection fractions, pulmonary and other blood volumes, and left ventricular dv/dt (from a continuous recording of the instantaneous change in left ventricular volume). 5) Comparison of these non-invasive radiocardiographic measurements to results available from contrast ventriculography in the cardiac catheterization laboratory.